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IMMUNE SYSTEM AND DISEASE INNATE AND ADAPTIVE IMMUNITY MECHANISMS OF PATHOGENICITY • Pathogenicity: The ability to cause • disease • Virulence: The extent of pathogenicity PORTALS OF ENTRY • • • • • Mucous membranes Skin Blood Respiratory tract Gastrointestinal tract MECHANISMS OF PATHOGENICITY Figure 15.9 THE CONCEPT OF IMMUNITY • • • • Susceptibility: Lack of resistance to a disease Immunity: Ability to ward off disease Innate immunity: Defenses against any pathogen Adaptive immunity: Immunity, resistance to a specific pathogen AN OVERVIEW OF THE BODY’S DEFENSES • Innate immunity: Defenses against any pathogen • Adaptive immunity: Induced resistance to a specific pathogen Figure 16.1 FIRST LINE OF DEFENSE INNATE (NON -SPECIFIC) IMMUNITY PHYSICAL FACTORS • Skin • Epidermis consists of tightly packed cells with • Keratin, a protective waterproof protein • Mucous membranes • Mucus: Traps microbes • Ciliary escalator: Microbes trapped in mucus are transported away from the lungs Figure 16.2 CILIARY ESCALATOR Figure 16.4 CILIARY ESCALATOR Figure 24.7 PHYSICAL/CHEMICAL FACTORS • Lacrimal apparatus: Washes eye • Saliva: Washes microbes off • Urine: Flows out • Vaginal secretions: Flow out CHEMICAL FACTORS • • • • • Fungistatic fatty acid in sebum Low pH (3–5) of skin Lysozyme in perspiration, tears, saliva, and urine Low pH (1.2–3.0) of gastric juice Low pH (3–5) of vaginal secretions GENETIC RESISTANCE • Some individuals may have enough of a genetic difference that will allow them to be immune to a specific pathogen. • Ex: Humans carrying a gene for sickle-cell anemia are immune to malaria! • Other examples: leprosy, tuberculosis (20% exposed are resistant), certain fungal infections • Asymptomatic carriers – Herpes simplex SECOND LINE OF DEFENSE INNATE (MAINLY NON -SPECIFIC) FORMED ELEMENTS IN BLOOD FUNCTION Red Blood Cells Transport O2 and CO2 White Blood Cells: Neutrophils Phagocytosis Basophiles Histamine Eosinophils Kill parasites CELL MORPHOLOGY FORMED ELEMENTS IN BLOOD FUNCTION Monocytes Phagocytosis Dendritic cells Phagocytosis Natural killer cells Destroy target cells CELL MORPHOLOGY FORMED ELEMENTS IN BLOOD FUNCTION T cells Cell-mediated immunity B cells Produce antibodies Platelets Blood clotting CELL MORPHOLOGY DIFFERENTIAL WHITE CELL COUNT • Percentage of each type of white cell in a sample of 100 white blood cells Neutrophils 60–70% Basophils 0.5–1% Eosinophils 2–4% Monocytes 3–8% Lymphocytes (T and B cells) 20–25% DEVELOPMENT OF A MACROPHAGE PHAGOCYTOSIS • Phago: From Greek, meaning eat • Cyte: From Greek, meaning cell • Ingestion of microbes or particles by a cell, performed by phagocytes • Neutrophils • Fixed macrophages • Wandering macrophages VIDEO Figure 16.6 PHAGOCYTOSIS Figure 16.7 HOW DO WBC SURVEY AND RECOGNIZE? • PRRs – Patten Recognition Receptors • Protein located on surface of WBC • PAMPs – Pathogen Associated Molecular Pattern • Proteins, lipids, or carbs located on the pathogen that are distinguishable from other non-pathogenic cells such as: • Peptidoglycan, lipoteichoic acid, lipopolysaccharides, flagellin, zymosan, double stranded RNA, etc… • Adherence COMPONENTS OF LYMPHATIC SYSTEM Figure 16.5a MAJOR FUNCTIONS OF LYMPHATIC SYSTEM • 1. Provide a route for the extracellular fluid to return back to the circulatory system • 2. Acts a “drain off system” for inflammatory system • 3. Involved in immune response by transporting numerous WBC (esp. T & B cell, and antibodies) Imp differences from circulatory system: Lymph fluid travels only in ONE DIRECTION (extremities to heart) Lymph is moved only by contraction of the skeletal muscles THE LYMPHATIC SYSTEM Figure 16.5b–c INFLAMMATION Identifiable signs of inflammation: • Redness (rubor) • Swelling (tumor) • Pain (dolor) • Warmth (calor) • Acute-phase proteins activated (complement, cytokine, and kinins) • Vasodilation (histamine, prostaglandins, and leukotrienes) WHAT CAUSES AN INFLAMMATORY RESPONSE? • Tissue injury or death (physical – bump, fall, etc..) • Trauma from infection • Allergic reactions (diet or environmental factors) PRIMARY FUNCTION OF THE INFLAMMATORY RESPONSE • 1. mobilize and attract immune response to site of injury • 2. sets scene to repair tissue damage & clear away harmful substances • 3. destroy and block microbes from further invasion THE PROCESS OF INFLAMMATION Figure 16.8a, b PHAGOCYTE MIGRATION AND PHAGOCYTOSIS [Insert Animation Inflammation: Overview, Steps.] Figure 16.8c FEVER • Hypothalamus normally set at 37°C • Toxins from bacteria trigger the deregulation of the hypothalamus (exogenous pyrogen). Examples are endotoxins (remember them?). • Pyrogen – substance that causes a rise in body temp • Monocytes, neutrophils, and macrophages endogenous pyrogens as part of inflammatory response. (ex: macrophages -> interleukin 1 (IL-1) & tumor necrosis factor (TNF)). • Vasodilation and sweating: Body temperature falls FEVER • Advantages • Inhibits multiplication of temp sensitive microbes • Lower iron concentrations (nutrient used by some microbes that can limit their growth) • Speeds up immune response such as phagocytosis • Produces Interferons • Disadvantages • • • • Tachycardia Acidosis Dehydration 44–46°C fatal INTERFERONS (IFNS) • IFN- and IFN-: Cause cells to produce antiviral proteins that inhibit viral replication • Gamma IFN: Causes neutrophils and macrophages to phagocytize bacteria ANTIVIRAL ACTIONS OF INTERFERONS Figure 16.15 IMMUNE CELL TYPES (AGAIN…) Good site for review (click here)